Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata, Japan.
Department of Biosciences, Teikyo University, Utsunomiya, Tochigi, Japan.
Biosci Biotechnol Biochem. 2023 Dec 19;88(1):8-15. doi: 10.1093/bbb/zbad146.
Gibberellins are diterpenoid phytohormones that regulate plant growth, and are biosynthesized from a diterpene intermediate, ent-kaurene, which is produced from geranylgeranyl diphosphate via ent-copalyl diphosphate (ent-CDP). The successive 2 cyclization reactions are catalyzed by 2 distinct diterpene synthases, ent-CDP synthase (ent-CPS) and ent-kaurene synthase (KS). Various diterpene synthase genes involved in specialized metabolism were likely created through duplication and neofunctionalization of gibberellin-biosynthetic ent-CPS and KS genes in crops. Brachypodium distachyon is a monocotyledonous species that is a model plant in grasses. We herein found 1 ent-CPS gene homolog BdCPS and 4 tandemly arrayed KS-like genes BdKS1, KSL2, KSL3, and KSL4 in the B. distachyon genome, a simpler collection of paralogs than in crops. Phylogenetic and biochemical analyses showed that BdCPS and BdKS1 are responsible for gibberellin biosynthesis. BdKSL2 and BdKSL3 are suggested to be involved in specialized diterpenoid metabolism. Moreover, we restored KS activity of BdKSL2 through amino acid substitution.
赤霉素是二萜类植物激素，调节植物生长，由二萜中间体贝壳杉烯酸合成，贝壳杉烯酸由香叶基香叶基二磷酸通过对映贝壳杉烯酸二磷酸（ent-CDP）产生。连续的 2 个环化反应由 2 种不同的二萜合酶催化，ent-CDP 合酶（ent-CPS）和贝壳杉烯酸合酶（KS）。参与特殊代谢的各种二萜合酶基因可能是通过作物中赤霉素生物合成的 ent-CPS 和 KS 基因的重复和新功能化而产生的。Brachypodium distachyon 是单子叶植物，是禾本科植物的模式植物。我们在 B. distachyon 基因组中发现了 1 个 ent-CPS 基因同源物 BdCPS 和 4 个串联排列的 KS 样基因 BdKS1、KSL2、KSL3 和 KSL4，其基因家族比作物更简单。系统发育和生化分析表明，BdCPS 和 BdKS1 负责赤霉素的生物合成。BdKSL2 和 BdKSL3 可能参与特殊的二萜代谢。此外，我们通过氨基酸取代恢复了 BdKSL2 的 KS 活性。
